The recreational sport referred to as “Airsoft” is known, which consists of using replica weapons and projectiles for team games.
The power of the projectiles is limited in order to remain within the field of recreational and competitive sports games.
Many arrangements have been proposed over the years.
There are existing arrangements which use reserves of compressed gas to propel the projectile by means of a volume of pressurized gas released from the gas reserve on demand. These reserves may be of different sizes, but one of the problems is bulk. Either the volume is sufficient but the pressurized container is bulky, or cartridges of small volume are used but the possible number of shots is limited.
It is also necessary to fill the pressurized container or to buy cartridges, which is not very satisfactory.
Another arrangement which is very common and widely available commercially is based on electromechanical means. These electromechanical means comprise an electric motor and a set of gears driven by said motor, referred to as a “gear box”. These gears have two functions: one is to feed a projectile to a thrust nose, and the other is to propel said projectile from the thrust nose using pressurized air.
The thrust nose is a hollow tube, sealingly connected to a fixed pressure chamber. This assembly is intended to be housed in a replica weapon.
The thrust nose can be in two positions, a rearward position allowing insertion of a pellet in front of said thrust nose, and a forward position where the thrust nose introduces the projectile into the barrel of the replica weapon.
This projectile, usually a pellet, comes from a reserve into its position in front of the thrust nose.
The fixed pressure chamber comprises a piston, movable in translation within said fixed pressure chamber. The front part of the movable piston carries means to form a seal with the fixed chamber within which it is movable in translation. The rear of the piston bears against one end of a spring interposed between the rear of said piston, the other end of the spring bearing against the bottom of a housing containing all the electromagnetic means.
The gears and the motor move the piston within the fixed pressure chamber towards the rear of the chamber, generally by means of a rack, which compresses the spring, and when the piston is moved back translationally as far as possible, the spring is simultaneously also compressed as much as possible.
The gear driving the piston is provided with a toothless pad, so that when it is rotated, immediately after maximum compression, said gear releases the piston which is then propelled forwards into the chamber by the relaxation of the spring. This displacement compresses the air in said chamber. This greatly accelerates the air in the thrust nose and this air then propels the projectile, in this case the pellet in the barrel. This mechanism is highly attractive because it uses electrical energy that can be stored in cells or batteries for powering the motor.
This type of energy is very practical, easily available, and easily rechargeable, with good autonomy. However, the thrust is directly dependent on the spring and it is known that a spring has properties which vary over time and which vary with the temperature. A spring has a major disadvantage: it releases a thrust that is irregular, with high power at the beginning of the thrust and fading at the end of its travel.
Finally, the electromechanical means consume large amounts of energy, particularly due to friction.
Instead it would be helpful to have either a constant released force or a progressively released force in order to launch the pellet by overcoming the inertia and accelerating said pellet once it is in motion, in other words controlling the acceleration of the pellet in order to optimize the transfer of energy.
Similarly, the release of the spring/piston as well the stopping of the spring/piston at the end of travel leads to an evident lack of flexibility, affecting the accuracy of the shot to say nothing of the discomfort for the shooter.